DE102005045888B3 - Operating device for internal combustion engine has Lambda regulator, trimming regulator and setting signal unit - Google Patents

Abstract

The operating device includes a Lambda regulator dependent on a first measuring signal (MS1) for the first exhaust gas probe, which reports a Lambda correction factor (LAMCOR). A the trimming regulator is supplied with the regulating difference (DMS2) between the intended an actual values of a second measuring signal for the second exhaust gas probe, and produces a proportional correction factor (PCORTRIM). The setting signal unit reports the fuel in the cylinder by a setting signal (SG).

Description

The The invention relates to a device for operating an internal combustion engine.

always stricter legal regulations make it in internal combustion engines on the one hand, the raw emissions as much as possible lower, d. H. to reduce pollutant emissions during combustion of the air / fuel mixture incurred in the cylinders. On the other hand are in internal combustion engines Exhaust after-treatment systems in use, pollutant emissions, the while the combustion process of the air / fuel mixture in the cylinders be generated in harmless Convert substances. In particular, in gasoline engines come to this than Catalytic converters Three-way catalysts in use. High efficiency in the conversion of pollutant components, which are carbon monoxide, hydrocarbons or nitrogen oxides, sets a precise pre-set air / fuel ratio in the cylinders and further, the mixture upstream of the catalytic converter must have a have predetermined variation, d. H. a targeted operation of the Internal combustion engine both in excess air and in lack of air is necessary to fill and to ensure emptying of the oxygen storage of the catalytic converter. In the storage of oxygen in particular the nitrogen oxides reduced while when emptying the oxidation is supported and further prevented is that inlaid oxygen molecules disable portions of the catalytic converter.

Out the textbook "Handbook Engine " Editor Richard von Basshuysen / Fred Schäfer, second edition, June 2004, Friedrich Vieweg & son Verlagsgesellschaft mbH Braunschweig / Wiesbaden, page 559, is one Lambda control for an internal combustion engine known with an exhaust gas probe, which is a binary lambda probe is formed and the upstream of a catalytic converter is arranged in an exhaust tract of an internal combustion engine. Further Also, another exhaust gas probe is provided downstream of the catalytic converter. The lambda control includes a PI controller, with the P and I components in maps about the engine speed and load are stored. An excitation of the catalytic converter, Lambda fluctuation, results from two-point control due to the binary Measurement signal of the upstream lambda probe. The control is designed so that the amplitude of lambda fluctuations be set to about 3%. For better compliance with a lambda window upstream of the catalytic converter is a superimposed trim control over a binary Nachkatsonde intended.

Of the reason for the provision of a trim control is that exhaust probes, in particular the upstream the catalytic converter are arranged, their response to changes of the air / fuel ratio change during its service life. this leads to in that, based on the measuring signal of the exhaust gas probe, either changes in the Air / fuel ratio earlier or later recognizable are. In particular, the response of the exhaust gas probe at the jumps of her Measurement signal from a fat value to a lean value and vice versa also change asymmetrically. The Lean value takes the measurement signal of the binary lambda probe, if the Air / fuel ratio is larger as a stoichiometric Air / fuel ratio. The measurement signal of the binary Lambda probe has a grease value when the air / fuel ratio is smaller is as a stoichiometric air / fuel ratio, wherein the ratios in each case based on the composition of the mixture before Oxidation of the fuel.

If the lambda control does not respond to the changed response of the Flue gas probe is adjusted, so it may lead to increased pollutant emissions Internal combustion engine come due to a greatly reduced conversion pollutant emissions into harmless substances. For this purpose attacks the trim control.

To the Ensure that according to specified maximum pollutant emissions not exceeded are diagnoses of components of the exhaust tract of the internal combustion engine often through regulated by law. So z. B. an oxygen storage capacity of the catalytic converter to diagnose.

From the DE 103 07 010 B3 it is known to diagnose the exhaust gas catalyst, as soon as during a lean half period a change from a rich to a lean fuel mixture has been detected, first to keep the lambda control factor constant for a residence time and to further reduce it by a proportional jump after the residence time. The maximum value of the lambda control factor is maintained until a defined oxygen charge has been reached in this control cycle. The particular oxygen load used to perform the catalyst efficiency diagnostics corresponds to the oxygen storage capability of an aged catalyst that is just meeting the requirements that are prescribed. The efficiency diagnosis is carried out with the aid of a lambda monitor probe, which is mounted in the exhaust gas flow downstream of the catalytic converter. The monitor probe detects whether a constant lambda value is reached or whether the lambda value varies according to the control cycles. Varies by the monitor probe ge measured lambda value, so the tested catalyst does not have sufficient oxygen storage capacity, and a defective or aged catalyst is detected.

In the DE 196 06 652 A1 A method for adjusting the air / fuel ratio for a catalytic converter with a downstream catalytic converter is described. In this method, the oxygen components contained in the exhaust gas of the internal combustion engine upstream and downstream of the catalyst are detected and the adjustment of the air / air ratio is influenced, wherein the method is characterized by the fact that from the oxygen components mentioned a measure of the instantaneous oxygen filling level of the catalyst model is determined. From the model parameters statements about the aging state of the catalyst are derived and the air / fuel ratio adjusted so that the oxygen filling level of the catalyst is maintained at a constant average level.

In the DE 102 23 554 C1 a method for diagnosing a broadband λ-probe is described, which is arranged in the exhaust tract of an internal combustion engine and outputs an output signal, wherein an air-fuel ratio with which the internal combustion engine is operated, starting from a desired value, a periodic change with a superimposed on certain forced excitation frequency and during which the output signal is detected and therefrom generates a state of the λ-probe indicating diagnostic value, the predetermined forced excitation frequency from a start value he lowers until the output signal reaches a predetermined threshold and from the then present frequency Value of the Forced Excitation Frequency generates the diagnostic value.

From the DE 10 2004 033 325 A1 a diagnostic device for an exhaust gas sensor is known. This device for diagnosing a fault by deterioration of an exhaust gas sensor has a larger detection accuracy by another range for detecting the deterioration of the exhaust gas sensor. An exhaust gas sensor is disposed in an exhaust pipe of an internal combustion engine to produce an output corresponding to the components of the exhaust gas of the engine. The apparatus has means for generating a detection signal that is multiplied by a fuel injection amount used in normal operation to provide a fuel injection amount to be used for determining a state of the exhaust gas sensor. The apparatus includes means for extracting a frequency response corresponding to the detection signal from an exhaust gas sensor output. The output is a function of the calculated fuel injection quantity. The condition of the exhaust gas sensor is determined based on the extracted frequency response.

task The invention is an apparatus for operating an internal combustion engine to create an operation with very low pollutant emissions allows wherein also an operating state of a diagnosis of the exhaust tract considered component to be assigned should be.

The Task is solved by the characteristics of the independent Claim. Advantageous embodiments of the invention are in the subclaims characterized.

The Invention is characterized by a device for operating an internal combustion engine having at least one cylinder and a Exhaust tract in which an exhaust gas catalyst, a first exhaust gas probe upstream of the Catalytic converter and a second exhaust gas probe downstream of the Catalytic converter are arranged. The device has a lambda controller who is trained depending on a first measurement signal associated with the first exhaust probe, a lambda correction contribution to investigate. Furthermore, a trim controller is provided as a control difference a desired value and an actual value of a second measuring signal are supplied, that is associated with the second exhaust gas probe and that is configured to determine a proportional correction contribution. The first exhaust gas probe is preferably a binary one Exhaust probe, but it can in principle also a linear exhaust gas probe be. It is particularly easy if the second exhaust gas probe a binary exhaust gas probe is, but she can, in principle also be a linear exhaust gas probe.

Furthermore, an actuating signal unit is provided, which is designed to determine an actuating signal for metering fuel into the cylinder as a function of the lambda correction contribution and, in an operating state of a diagnosis of the component assigned to the exhaust tract, additionally depending on the proportional correction contribution the actuating signal for metering fuel to determine in the cylinder. The component assigned to the exhaust gas tract may be, for example, the exhaust gas catalytic converter, the first or the second exhaust gas probe or else a further component. Characterized in that the control signal in the control signal unit in the operating state of the diagnosis is additionally determined as a function of the proportional correction contribution, a temporally very fast penetration of the trim controller is ensured on the fuel to be metered. This leads in particular for relatively long control cycles, as in particular in the diagnosis and here in particular in connection with the use of egg ner binary first exhaust gas probe occur, significantly reduced emissions of pollutants also during the diagnosis. Moreover, it has surprisingly been found that even so the diagnosis can be made much more precise.

According to one Advantageous embodiment, the device comprises a low-pass filter for filtering the actual value of the second measuring signal and for supplying the filtered actual value of the second measurement signal to the trim controller for forming the control difference in the operating state of the diagnosis a component associated with the exhaust tract. In this way, especially for a suitable choice one for the cut-off frequency of the low-pass filter representative Size, one Very good decoupling of the trim controller from the to be performed Diagnosis guaranteed become. In this way, the diagnosis can then be carried out with particular precision and on the other hand by the trim controller particularly precise changes in the response the first exhaust gas probe can be compensated.

Especially It is advantageous if the operating state of the diagnosis the exhaust system associated component an operating state of the diagnosis of the catalytic converter is.

embodiments The invention are explained in more detail below with reference to the schematic drawings. It demonstrate:

1 an internal combustion engine with a control device,

2 a block diagram of a part of the control device and

3 a waveform.

An internal combustion engine ( 1 ) comprises an intake tract 1 , an engine block 2 , a cylinder head 3 and an exhaust tract 4 , The intake tract 1 preferably includes a throttle 5 and a collector 6 and a suction tube 7 leading to a cylinder Z1 via an inlet passage in the engine block 2 is guided. The engine block 2 further comprises a crankshaft 8th , which has a connecting rod 10 with the piston 11 of the cylinder Z1 is coupled.

The cylinder head 3 includes a valvetrain with a gas inlet valve 12 and a gas outlet valve 13 , The cylinder head 3 further comprises an injection valve 18 and a spark plug 19 , Alternatively, the injection valve 18 also in the intake manifold 7 be arranged.

In the exhaust tract is an exhaust gas catalyst 21 arranged, which is designed as a three-way catalyst. Further, in the exhaust tract, a further exhaust gas catalyst can be arranged, which is designed as a NOx catalyst.

A control device 25 is provided, the sensors are assigned, which detect different parameters and each determine the value of the measured variable. The control device 25 determined depending on at least one of the measured variables manipulated variables, which are then converted into one or more control signals for controlling the actuators by means of appropriate actuators. The control device 25 may also be referred to as a device for operating the internal combustion engine.

The sensors are a pedal position transmitter 26 , which is an accelerator pedal position of an accelerator pedal 27 detected, an air mass sensor 28 , which is an air mass flow upstream of the throttle 5 detected, a temperature sensor 32 , which detects an intake air temperature, an intake manifold pressure sensor 34 , which is an intake manifold pressure in the collector 6 detected, a crankshaft angle sensor 36 , which detects a crankshaft angle, which then a speed N is assigned.

Furthermore, a first exhaust gas probe 42 provided upstream of the catalytic converter 21 is arranged and which detects a residual oxygen content of the exhaust gas and whose measurement signal MS1 is characteristic of the air / fuel ratio in the combustion chamber of the cylinder Z1 and upstream of the first exhaust gas probe 42 before the oxidation of the fuel, hereinafter referred to as the air / fuel ratio in the cylinders Z1-Z4. Furthermore, a second exhaust gas probe 43 provided downstream of the catalytic converter 21 is arranged and the detected a residual oxygen content of the exhaust gas and whose measurement signal, namely the actual value MS2 of the measurement signal, is characteristic of the air / fuel ratio in the combustion chamber of the cylinder Z1 and upstream of the second exhaust gas probe 43 before the oxidation of the fuel, hereinafter referred to as the air-fuel ratio downstream of the catalytic converter.

The first exhaust gas probe 42 is preferably a binary lambda probe. The second exhaust gas probe 43 is preferably a binary lambda probe. However, the first and / or the second exhaust gas probe may in principle also be a linear lambda probe.

ever according to embodiment The invention may be any subset of said sensors be present or it can also additional Sensors be present.

The actuators are, for example, the Dros selklappe 5 , the gas inlet and outlet valves 12 . 13 , the injection valve 18 or the spark plug 19 ,

Next The cylinder Z1 are preferably also further cylinders Z2 to Z4 provided, which then also corresponding actuators and possibly Sensors are assigned.

A part of the control device 25 is based on the block diagram of the 2 shown in more detail. A block B1 comprises a lambda controller. The lambda controller is supplied with the first measurement signal MS1 as a controlled variable. The measurement signal MS1 is preferably binary in nature, ie it assumes a lean value when the air / fuel ratio before the catalytic converter 21 is lean and a fat value when it's fat. Only in a very small intermediate range does it also take intermediate values between the lean and the fat value. Due to the binary nature of the first measurement signal MS1, the lambda controller is designed as a two-point controller. The lambda controller is preferably designed as a PI controller. A P component is preferably supplied as a proportional jump P_J to block B1. A block B2 is provided in which, depending on the rotational speed N and a load variable LOAD, the proportional jump P_J is determined. For this purpose, a map is preferably provided, which can be permanently stored.

One I component of the lambda controller is preferably dependent on an integral increment I_INC determined. The integral increment I_INC is preferred in one Block B3 also dependent determined by the speed and a load size. This can also be, for example a map should be provided. The load size LOAD can be, for example be an air mass flow or the intake manifold pressure.

Furthermore is the input parameter for Block B1 also has a delay time T_D provided, which is determined in a block B5, which is below even closer explained is.

On the output side of the lambda controller, a lambda correction contribution LAM_COR is pending.

The mode of operation of the lambda controller in block B1 is exemplary with reference to FIG 3 explained in more detail. At a time t0, the lambda correction contribution LAM_COR has a neutral value, for example 1, and is increased starting from the time t0 until a time t1 as a function of the integral increment I_INC. For example, this is done in a predetermined time grid, in each of which the current value of the lambda correction contribution LAM_COR is increased by the integral increment I_INC. The time t1 is characterized in that the first measurement signal MS1 jumps from its lean value to its rich value.

is recognized that the first measurement signal MS1 of its lean value on the fat value has jumped, then the lambda correction contribution LAM_COR does not continue is incremented with the integral increment I_INC, but its value for the Delay period Retain T_D. With expiration of the delay period T_D, what to At time t2, the lambda correction contribution becomes decreased according to the proportional jump P_J. After the jump the lambda correction contribution LAM_COR at time t2, the lambda correction contribution LAM_COR then becomes reduced with the integral increment I_INC, preferably with a predetermined by the integral increment I_INC rate until the first measurement signal MS1 makes a jump from the fat value to the Lean value, which is the case at time t3. From the time Starting from t3, the lambda correction contribution LAM_COR remains for the given one Delay period T_D are at its value before it expires at the end of the delay period T_D, at a time t4 to the proportional jump P_J is increased again. Subsequently is again an increment of the lambda correction contribution LAM_COR depending on the integral increment I_INC. This basic functioning of the Lambda controller is independent of whether an operating state of a diagnosis of the exhaust tract assigned component is taken or not.

An actuating signal unit is formed by blocks B7, B9, B11 and a multiplication point M1. The actuating signal unit is designed to determine an actuating signal SG for metering fuel to the respective cylinder Z1 to Z4 as a function of the lambda correction contribution LAM_COR. By means of the control signal SG, the injection valve is preferred 18 driven.

In block B7, a lambda control factor LAM_FAC is determined as a function of the lambda correction contribution LAM_COR. For example, in an operating state outside the diagnosis of a component assigned to the exhaust tract, the lambda correction contribution LAM_COR is assigned directly to the lambda control factor LAM_FAC. In a multiplication point M1, a corrected fuel mass MFF_COR to be metered is determined by multiplying the lambda control factor LAM_FAC by a fuel mass MFF to be metered. The fuel mass to be metered is preferably determined in a block B9 as a function of the rotational speed N and the load size LOAD. This can be done for example with the aid of a map, which is preferably permanently stored. In block B11, the actuating signal SG is determined as a function of the corrected fuel mass MFF_COR to be metered. For this purpose, in the block B11, for example, an injection period can be determined and the control signal can be determined in accordance with the on injection valve for the injection period to meter fuel.

One Trim controller includes blocks B13 and B15. A block B17 is provided, whose entrance with a Actual value MS2 of the second measurement signal is applied. The block B17 comprises a low-pass filter for filtering the actual value MS2 of the second measurement signal and thus generates a filtered actual value MS2_FIL of the second measurement signal. A reference MS2_REF of the second measurement signal forms the setpoint of the second measurement signal. In a summation point S1 is formed by taking the difference of the reference MS2_REF and the Actual value MS2_FIL of the second measurement signal is a control difference DMS2 of the trim controller determined. The reference MS2_REF thus forms the Reference value of the second measuring signal. The filtering preferably takes place the actual value MS2 of the second measuring signal by a moving averaging, wherein preferably for filtering each new actual value MS2 of the second Measuring signal is weighted at about 10%, while the old filtered actual value MS2_FIL is weighted at about 90%. Through the moving averaging let yourself particularly easy to implement a low-pass filter. Depends on the Control difference D_MS2, in particular dependent on an integral over the Control difference, the block B13 is adapted to a trim delay time duration contribution T_D_COR_TRIM to determine. In block B5 then becomes dependent on the trim delay time contribution T_D_COR_TRIM and optionally an adaptation delay time duration contribution T_D_AD and optionally a diagnostic delay time duration contribution T_D_DIAG the delay period T_D, preferably determined by summation of the corresponding contributions. The adaptation delay time duration contribution is preferred T_D_AD dependent from the trim delay time contribution T_D_DIAG determined. This is preferably done outside the operating state the catalyst diagnosis. However, it can in principle also during the Diagnosis of a component of the exhaust tract done.

The diagnostic delay time contribution T_D_DIAG is determined in a block B15 that is configured to perform a diagnosis of a component associated with the exhaust tract. The component can, for example, the Abgaskatalysa gate 21 be. However, it can also, for example, the first exhaust gas probe 42 or the second exhaust gas probe 43 be. For the diagnosis of the catalytic converter 21 In the block B15, the diagnosis delay time duration contribution T_D_DIAG and preferably a diagnosis proportional contribution contribution DELTA_P are determined. This is done in such a way that it is possible to check whether the exhaust gas catalytic converter is functioning by pressurizing the lambda controller with the diagnostic delay time duration contribution T_D_DIAG and the diagnostic proportioning contribution DELTA_P 21 has an oxygen storage capability that has an aged catalytic converter that is just within allowable limits.

The addition of the lambda controller in addition to the diagnostic delay time duration contribution T_D_DIAG in the context of the diagnosis has the consequence that the control cycles of the lambda controller are significantly prolonged, as shown by the 3 is apparent. At a time t5, the first measurement signal MS1 jumps from its lean value to its richness value. A time period between times t5 and t6 corresponds to the delay period T_D outside the operating state of the diagnosis of the catalytic converter. During the operating state of the diagnosis, the delay time T_D is extended by the diagnostic delay time duration contribution T_D_DIAG. In this way, an increased fluctuation range of the degree of oxygen loading of the exhaust gas catalyst 21 reached. During the delay time period T_D, in the operating state of the diagnosis, a jump of the lambda correction contribution LAM_COR can also take place in accordance with the diagnostic proportioning contribution DELTA_P. Also by this measure, the predetermined oxygen loading can be well adjusted during the diagnosis. Preferred is in the control device 25 a characteristic course of the second measurement signal, and indeed its actual value, stored as a comparison course by appropriate tests with a suitably aged catalytic converter, for example on an engine test bench.

The actual value MS2 of the second measurement signal is then determined during the diagnosis in the block B15 compared with the comparison curve and, depending on this comparison, a quality value which is then representative of the deviation between the actual value MS2 of the second measurement signal and the comparison profile. For example, for this purpose, the amount of the difference of the actual value MS2 and the reference curve can be integrated and optionally normalized. Depending on this quality value, a diagnostic value DIAG_V is then determined in block B15. This can be done for example by repeatedly determining the quality value in different control cycles, such. 20, and summing the quality values and then comparing them with a predetermined threshold, which is predetermined such that, for example, when the threshold value is exceeded, the oxygen storage capacity of the catalytic converter 21 no longer corresponds to that of the boundary catalyst, ie this falls below.

In block B16, which forms the P component of the trim controller, a proportional correction contribution P_COR_TRIM is determined as a function of the control difference DMS2 of the trim controller. The proportion nal correction contribution P_COR_TRIM is proportional to the control difference DMS2 of the trim controller. The corresponding proportional parameter of the trim controller, as well as a corresponding integral parameter of the trim controller, can also be predefined as a function of, for example, the rotational speed and / or the load variable LOAD.

During the operating state of the diagnosis of a component assigned to the exhaust tract, block B7 is acted upon by the proportional correction contribution P_COR_TRIM. Thus, during the diagnosis, the lambda control factor LAM_FAC is additionally determined as a function of the proportional correction contribution P_COR_TRIM. This has the consequence that an occurring control difference DMS2 of the trim controller extremely promptly in an adjustment of the lambda control factor LAM_FAC and thus the actuating signal for metering the fuel. In this way, also during the diagnosis detected changes in the response of the first exhaust gas probe 42 be compensated very promptly. This is particularly important during the diagnosis since, due to the extended delay time T_D compared to an operating state without diagnosis, otherwise the intervention of the trim controller can only take place considerably later in time, and thus possibly an unstable control behavior can occur due to the high dead time. This is all the more reinforced, as during the diagnosis, the fluctuation in the oxygen load of the catalytic converter is particularly pronounced.

Outside the operating state of the diagnosis, the proportional correction contribution P_COR_TRIM the delay time period T_D added instead of being fed directly into block B7.

During the operating state of the diagnosis, the lambda correction contribution LAM_COR and the proportional correction contribution P_COR_TRIM can be linked to each other in an additive or multiplicative manner and optionally weighted to the lambda control factor LAM_FAC. Furthermore, the proportional correction contribution in the operating state of the diagnosis can also be used alternatively or additionally for determining the fuel mass MFF to be metered in block B9 or else for determining the actuating signal in block B11. Thus, for example, depending on the proportional correction contribution P_COR_TRIM an injection period of the respective injection valve 18 be modified.

The For example, reference MS2_REF may be fixed but is preferably different predetermined for the operating state of the diagnosis in comparison to operating states outside the diagnosis. For example, the reference MS2_REF is the corresponding one Grease or lean value or in particular in the operating state of Diagnosis also a suitably predetermined intermediate value, for example by observing the actual value MS2 of the second measuring signal during the preceding Diagnoses can be determined.

Furthermore can the delay time period T_D, the proportional increment P_J, the integral increment I_INC, the Diagnostic proportion jump contribution DELTA_P, the diagnostic delay time period contribution T_D_DIAG, the trim delay time period contribution T_D_COR_TRIM, the adaptation delay time duration contribution T_D_AD and possibly also the proportional correction contribution P_COR_TRIM for the lean or the rich periods of the lambda controller can be determined differently.

Outside The operating state of the diagnosis can be the control difference DMS2 of the Trim controller, for example, without filtering the actual value MS2 be formed of the second measurement signal.

Claims (3)

Device for operating an internal combustion engine having at least one cylinder (Z1 to Z4) and an exhaust gas tract ( 4 ), in which an exhaust gas catalyst ( 21 ), a first exhaust gas probe ( 42 ) upstream of the catalytic converter and a second exhaust gas probe ( 43 ) downstream of the catalytic converter ( 21 ), wherein the device comprises: a lambda controller, which is designed as a function of a first measuring signal (MS1), that of the first exhaust gas probe ( 42 ) is assigned to determine a lambda correction contribution (LAM_COR), - a trim controller, to which a nominal value and an actual value of a second measurement signal, which is assigned to the second exhaust gas probe and which is designed to generate a proportional difference (DMS2), are supplied. Correction contribution (P_COR_TRIM) to determine, - an actuating signal unit which is designed, depending on the lambda correction contribution (LAM_COR) to determine a control signal (SG) for metering fuel into the cylinder and in an operating state of a diagnosis of the exhaust tract ( 4 ) assigned component additionally depending on the proportional correction contribution (P_COR_TRIM) to determine the actuating signal for metering fuel into the cylinder. Device according to Claim 1, in which a low-pass filter is provided for filtering the actual value (MS2) of the second measuring signal and for supplying the filtered actual value (MS2_FIL) of the second measuring signal to the trimming controller for forming the control difference (DMS2) in the operating state of the diagnosis of the Exhaust tract ( 4 ) associated component. Device according to one of the preceding claims, in which the operating state of the diagnosis of the exhaust tract ( 4 ) assigned to an operating state of the diagnosis of the catalytic converter ( 21 ).